David,
I don't see much need for a correction factor for a mic if you have access
to spacer or gage blocks. Just set up the needed value on the spacer or gage
blocks, see what the mic reads, and then measure the unknown. You will at
least know if you are over or under. If it is just a few thou, then I would
trust the mic to give me this difference.
Rick
-----Original Message-----
From: gingery_machines@yahoogroups.com
[mailto:gingery_machines@yahoogroups.com] On Behalf Of David Frantz
Sent: Monday, January 24, 2011 4:06 PM
To: gingery_machines@yahoogroups.com
Cc: gingery_machines@yahoogroups.com
Subject: Re: [gingery_machines] new article: How Accurate is Your
Micrometer?
I'm certain some people do. At least in the sense maintenance, cleaning &
such. For the smaller stuff such as a mic with worn out threads it may not
be worth it.
At one time Starret had a calibration / repair program, I would imagine that
they still do.
An interesting aside here, working in the optics industry requires the
measurement of radiuses to rather high precision. However you need to be
able to do that in an economical manner. Those measurements were often
done on "lower cost" interferometers with rather run of the mill slides and
glass scales. The software would scan the radius in question; then take
the data and compute the actual radius by fitting a curve and using the peak
value of that curve. This worked surprisingly well.
This might not be all that useful for flat surfaces. However it might be
useful in coming up with a correction factor for mics that can't be fixed or
tuned otherwise. That is to use a set of precise Gage blocks to come up
with a slope function.
There is one other problem though. Once you start to try to get
measurements below a thousands of an inch you really need to start to
consider thermal and physical factors. Everything needs to be stabilized
temperature wise to even bother with a calibration effort.
David A Frantz
http://groups.yahoo.com/group/gingery_machines/app/peoplemap/view/map
No comments:
Post a Comment